Esophagus

Esophageal Inlet

The high-pressure zone at the inlet of the esophagus is the UES, which anatomically marks the end of a complex configuration of muscles that begins in the larynx and posterior pharynx and ends in the neck. The pharyngeal constrictor muscles are three consecutive muscles that begin at the base of the palate and end at the crest of the esophagus. The superior and middle pharyngeal constrictor muscles, as well as the oblique, transverse, and posterior cricoarytenoid muscles, are immediately proximal to the UES and serve to anchor the pharynx and larynx to structures in the mouth and palate. These muscles also aid in deglutition and speech but are not responsible for the high pressures noted in the UES. The inferior pharyngeal constrictor muscle is the final bridge between the pharyngeal and esophageal musculature.

Inserting into the median pharyngeal raphe, the inferior pharyngeal constrictor muscle is composed of two consecutive muscle beds—the thyropharyngeus and cricopharyngeus muscles—that originate bilaterally from the lateral portions of the thyroid and cricoid cartilages, respectively. The transition between the oblique fibers of the thyropharyngeus muscle and the horizontal fibers of the cricopharyngeus muscle creates a point of potential weakness, known as Killian triangle (site of a Zenker diverticulum). The cricopharyngeus muscle is responsible for generating a high-pressure zone that marks the position of the UES and esophageal introitus. Its distinctive bowing array of muscle fibers is unique and serves to transition into the circular esophageal musculature. This point of transition is flanked by the longitudinal esophageal muscles that extend superiorly to attach to the midportion of the posterior surface of the cricoid cartilage and form the V-shaped area of Laimer.

Esophageal Layers

The esophagus is comprised of two proper layers, the mucosa and muscularis propria. It is distinguished from the other layers of the alimentary tract by its lack of a serosa. The mucosa is the innermost layer and consists of squamous epithelium for most of its course. The distal 1 to 2 cm of esophageal mucosa transitions to cardiac mucosa or junctional columnar epithelium at a point known as the Z-line ( Fig. 42.2 ). Within the mucosa, there are four distinct layers: the epithelium, basement membrane, lamina propria, and muscularis mucosae. Deep to the muscularis mucosae lays the submucosa ( Fig. 42.3 ). Within it is a plush network of lymphatic and vascular structures, as well as mucous glands and Meissner neural plexus.

Enveloping the mucosa, directly abutting the submucosa, is the muscularis propria. Below the cricopharyngeus muscle, the esophagus is composed of two concentric muscle bundles: an inner circular and outer longitudinal ( Fig. 42.4 ). Both layers of the upper third of the esophagus are striated, whereas the layers of the lower two-thirds are smooth muscle. The circular muscles are an extension of the cricopharyngeus muscle and traverse through the thoracic cavity into the abdomen, where they become the middle circular muscles of the lesser curvature of the stomach. The collar of Helvetius marks the transition of the circular muscles of the esophagus to oblique muscles of the stomach at the incisura (cardiac notch). Between the layers of esophageal muscle is a thin septum comprised of connective tissue, blood vessels, and an interconnected network of ganglia known as Auerbach plexus. Enshrouding the inner circular layer, the longitudinal muscles of the esophagus begin at the cricoid cartilage and extend into the abdomen, where they join the longitudinal musculature of the cardia of the stomach. The esophagus is then wrapped by a layer of fibroalveolar adventitia.

Anatomic Narrowing

The esophageal silhouette resembles an hourglass. There are three distinct areas of narrowing that contribute to its shape. Measuring 14 mm in diameter, the cricopharyngeus muscle is the narrowest point of the gastrointestinal tract and marks the superiormost portion of the hourglass-shaped esophagus. Located just below the carina, where the left mainstem bronchus and aorta abut the esophagus, the bronchoaortic constriction at the level of the fourth thoracic vertebra creates the center narrowing and measures 15 to 17 mm. Finally, the diaphragmatic constriction, measuring 16 to 19 mm, marks the inferior portion of the hourglass and is located where the esophagus passes through the diaphragm. Between these three distinct areas of anatomic constriction are two areas of dilatation known as the superior and inferior dilatations. Within these areas, the esophagus resumes the normal diameter for an adult and measures approximately 2.5 cm.

Gastroesophageal Junction

The UES and LES mark the entrance and exit to the esophagus, respectively. These sphincters are defined by a high-pressure zone but can be difficult to identify anatomically. The UES corresponds reliably to the cricopharyngeus muscle, but the LES is more complex to discern. There are four anatomic points that identify the gastroesophageal junction (GEJ): two endoscopic and two external. Endoscopically, there are two anatomic considerations that may be used to identify the GEJ. The squamocolumnar epithelial junction (Z-line) may mark the GEJ provided that the patient does not have a distal esophagus replaced by columnar-lined epithelium, as seen with Barrett esophagus. The transition from the smooth esophageal lining to the rugal folds of the stomach may also identify the GEJ accurately. Externally, the collar of Helvetius (or loop of Willis), where the circular muscular fibers of the esophagus join the oblique fibers of the stomach, and the gastroesophageal fat pad are consistent identifiers of the GEJ ( Fig. 42.5 ).

Vasculature

The rich vascular and lymphatic structures that nourish and drain the esophagus serve as a surgical safety net and a highway for metastases. The vasculature is divided into three segments: cervical, thoracic, and abdominal. The cervical esophagus receives most of its blood supply from the inferior thyroid arteries, which branch off of the thyrocervical trunk on the left and the subclavian artery on the right ( Fig. 42.6 ). The cricopharyngeus muscle, which marks the inlet of the esophagus, is supplied by the superior thyroid artery. The thoracic esophagus receives its blood supply directly from four to six esophageal arteries coming off the aorta, as well as esophageal branches off the right and left bronchial arteries. It is supplemented by descending branches off the inferior thyroid arteries, intercostal arteries, and ascending branches of the paired inferior phrenic arteries. The abdominal esophagus receives its blood supply from the left gastric artery and paired inferior phrenic arteries. All the arteries that supply blood to the esophagus terminate in a fine capillary network before they penetrate the muscular wall of the esophagus. After penetrating and supplying the muscular layers, the capillary network continues the length of the esophagus within the submucosal layer.

The venous drainage parallels the arterial vasculature and is just as complex. In all parts of the esophagus, the rich submucosal venous plexus is the first basin for venous drainage of the esophagus. In the cervical esophagus, the submucosal venous plexus drains into the inferior thyroid veins, which are tributaries of the left subclavian vein and right brachiocephalic vein ( Fig. 42.7 ). The drainage of the thoracic esophagus is more intricate. The submucosal venous plexus of the thoracic esophagus joins with the more superficial esophageal venous plexus and the venae comitantes that envelop the esophagus at this level. This plexus, in turn, drains into the azygos and hemiazygos veins on the right and left sides of the chest, respectively. The intercostal veins also drain into the azygos venous system. The abdominal esophagus drains into the systemic and portal venous systems through the left and right phrenic veins and left gastric (coronary) vein and short gastric veins, respectively.

Lymphatics

The lymphatic drainage of the esophagus is extensive; it consists of two interconnecting lymphatic plexuses arising from the submucosa and muscularis layers. The submucosal lymphatics penetrate the muscularis propria and drain into the plexus that runs longitudinally in the esophageal wall. They then egress and drain into regional lymph node beds. In the upper two-thirds of the esophagus, lymphatic flow is upward, whereas in the distal third, flow tends to be downward. Esophageal lymphatics begin in the neck with drainage to the paratracheal lymph nodes anteriorly and deep lateral cervical and internal jugular nodes laterally and posteriorly. Once inside the chest, the lymphatics form a matrix of interconnecting channels that drain into the mediastinal lymph nodes and thoracic duct. Anteriorly, the paratracheal and subcarinal lymph nodes and the paraesophageal, retrocardiac, and infracardiac nodes all drain the esophagus.

Other mediastinal stations, such as the para-aortic and inferior pulmonary ligament nodes, can also receive drainage from the thoracic esophagus. Posteriorly, nodes along the esophagus and azygos veins are the primary sites of drainage ( Fig. 42.8 ). The intricate lymphatic network of the esophagus allows for rapid spread of infection and tumor into three body cavities. It stands to reason that the rich arterial supply to the esophagus makes it one of the more durable organs in the body with respect to surgical manipulation, whereas its comprehensive venous and lymphatic drainage create an oncologic challenge to controlling cellular migration. These anatomic complexities lead to surgical challenges when treating esophageal cancer and other esophageal diseases.

Innervation

The innervation to the esophagus is sympathetic and parasympathetic ( Fig. 42.9 ). The cervical sympathetic trunk arises from the superior ganglion in the neck. It extends next to the esophagus into the thoracic cavity, where it terminates in the cervicothoracic (stellate) ganglion. Along the way, it gives off branches to the cervical esophagus. The thoracic sympathetic trunk continues on from the stellate ganglion, giving off branches to the esophageal plexus, which envelops the thoracic esophagus anteriorly and posteriorly. Inferiorly, the greater and lesser splanchnic nerves innervate the distal thoracic esophagus. In the abdomen, the sympathetic fibers lay posteriorly alongside the left gastric artery.

The parasympathetic fibers arise from the vagus nerve, which gives rise to the superior and recurrent laryngeal nerves. The superior laryngeal nerve branches into the external and internal laryngeal nerves that supply motor innervation to the inferior pharyngeal constrictor muscle and cricothyroid muscle and sensory innervation to the larynx, respectively ( Fig. 42.10 ). The right and left recurrent laryngeal nerves come off the vagus nerve and loop underneath the right subclavian artery and aortic arch, respectively. They then travel upward in the tracheoesophageal groove to enter the larynx laterally underneath the inferior pharyngeal constrictor muscle. Along the way, they innervate the cervical esophagus, including the cricopharyngeus muscle. Unilateral injury to the superior or recurrent laryngeal nerve results in hoarseness and aspiration from laryngeal and UES dysfunction. In the thorax, the vagus nerve sends fibers to the striated muscle and parasympathetic preganglionic fibers to the smooth muscle of the esophagus. A weblike nervous plexus envelops the esophagus throughout its thoracic extent. These sympathetic and parasympathetic fibers penetrate through the muscular wall, forming networks between the muscle layers to become Auerbach plexus and within the submucosal layer to become Meissner plexus ( Fig. 42.11 ). They provide an intrinsic autonomic nervous system within the esophageal wall that is responsible for peristalsis. The parasympathetic fibers coalesce 2 cm above the diaphragm into the left (anterior) and right (posterior) vagus nerves, which descend anteriorly onto the fundus and lesser curvature and posteriorly onto the celiac plexus, respectively.

Swallowing

There are three phases to swallowing: oral, pharyngeal, and esophageal. Six events occur during the oropharyngeal phase of swallowing ( Fig. 42.12 ). These rapid series of events last about 1.5 seconds and, once initiated, are completely reflexive.

• 1.

  Elevation of the tongue. Food is taken into the mouth and mixed with saliva to prepare a soft bolus for transport. The tongue pushes the bolus into the posterior oropharynx.

• 2.

  Posterior movement of the tongue. The tongue moves posteriorly and thrusts the food bolus into the hypopharynx.

• 3.

  Elevation of the soft palate. Simultaneously, as the tongue moves the food bolus into the hypopharynx, the soft palate is elevated to close off the passage into the nasopharynx.

• 4.

  Elevation of the hyoid. To help bring the epiglottis under the tongue, the hyoid bone moves anteriorly and upward.

• 5.

  Elevation of the larynx. The change in position of the hyoid elevates the larynx and opens up the retrolaryngeal space, further facilitating the movement of the epiglottis under the tongue.

• 6.

  Tilting of the epiglottis. Finally, the epiglottis tilts back, covering the opening of the larynx to prevent aspiration.

Esophageal Phase

Upper esophageal sphincter

The esophageal phase of swallowing is initiated by the actions during the pharyngeal phase. To allow passage of the food bolus, the UES relaxes and the peristaltic contractions of the posterior pharyngeal constrictors propel the bolus into the esophagus. The pressure differential generated between the positive pressure in the cervical esophagus and the negative intrathoracic pressure sucks the bolus into the thoracic esophagus. Within 0.5 second of the initiation of swallowing, the UES closes, reaching close to 90 mm Hg. This postrelaxation contraction lasts 2 to 5 msec, initiates peristalsis, and prevents reflux of the bolus back into the pharynx. The UES pressure returns to resting pressure (60 mm Hg) as the wave travels into the midesophagus ( Fig. 42.13 ).

Peristalsis

There are three types of esophageal contractions: primary, secondary, and tertiary. Primary peristaltic contractions are progressive and move down the esophagus at a rate of 2 to 4 cm/sec and reach the LES about 9 seconds after the initiation of swallowing ( Fig. 42.14 ). They generate an intraluminal pressure from 40 to 80 mm Hg. Successive swallows will follow with a similar peristaltic wave unless swallowing is repeated rapidly, at which time the esophagus will remain relaxed until the last swallow occurs, and peristalsis will follow. Secondary peristaltic contractions are also progressive but are generated from distention or irritation of the esophagus rather than voluntary swallowing. They can occur as an independent local reflex to clear the esophagus of material that was left behind after the progression of the primary peristaltic wave. Tertiary contractions are nonprogressive, nonperistaltic, monophasic or multiphasic, simultaneous waves that can occur after voluntary swallowing or spontaneously between swallows throughout the esophagus. They represent uncoordinated contractions of the smooth muscle that are responsible for esophageal spasm.

Lower esophageal sphincter

The final phase of esophageal bolus transit occurs through the LES. Although this is not a true sphincter, there is a distinct high-pressure zone that measures 2 to 5 cm in length and generates a resting pressure of 6 to 26 mm Hg. The LES is located in the chest and abdomen. A minimum total length of 2 cm, with at least 1 cm of intraabdominal length, is required for normal LES function. The transition from the intrathoracic to the intraabdominal sphincter is noted on a manometric tracing and is known as the respiratory inversion point (RIP; Fig. 42.15 ). At this point, the pressure of the esophagus changes from negative to positive with inspiration and positive to negative with expiration.

Peristaltic contractions alone do not generate enough force to open up the LES. Vagal-mediated relaxation of the LES occurs 1.5 to 2.5 seconds after pharyngeal swallowing and lasts 4 to 6 seconds. This flawlessly timed relaxation is needed to allow efficient transport of a food bolus out of the esophagus and into the stomach. A postrelaxation contraction of the LES occurs after the peristaltic wave has passed through the esophagus, allowing the LES to return to its baseline pressure ( Fig. 42.16 ), reestablishing a barrier to reflux.

Reflux Mechanism

Not all reflux is abnormal. Healthy individuals have occasional episodes of gastroesophageal reflux that is a result of spontaneous opening of the LES. The competence of the LES and its ability to establish a barrier to reflux depends on several factors: adequate pressure and length, radial symmetry, and motility of the esophagus and stomach. A competent sphincter is at least 2 cm and carries a pressure between 6 and 26 mm Hg. Radial asymmetry and abnormal peristalsis prevent proper closure and allow free refluxing of gastric material into the distal esophagus. Abnormal esophageal motility and poor gastric emptying result in inadequate esophageal clearance that also encourages reflux. Finally, neurotransmitters, hormones, and peptides that regulate the LES can increase or decrease tone. All these anatomic and physiologic disruptions can result in reflux through the LES and are implicated in the development of gastroesophageal reflux disease (GERD).

Diagnosis

Esophageal motility disorders constitute a relatively rare group of conditions, the underlying causes of which remain poorly understood. Patients with these conditions will present with a variety of symptoms including dysphagia, chest pain, heartburn, regurgitation, and weight loss. By definition, esophageal motility disorders are diagnosed when manometric findings exceed two standard deviations from normal. Unfortunately, symptom severity does not always correlate well with manometry, which is of critical importance in planning for surgical intervention in these generally complicated patients. Esophageal motility disorders are best classified by the Chicago classification, which was derived from data obtained by high-resolution manometry (HRM) with esophageal pressure topography ( Table 42.2 ). Because this classification is purely based on differentiating patterns of manometric findings, the exact clinical utility of this classification remains under investigation. Nevertheless, the findings from these ultramodern diagnostic modalities correlate well with those from conventional, water-perfused manometry. From a practical standpoint, the primary difference between HRM and conventional manometry is that in HRM, the pressure sensors are no more than 1 cm apart rather than every 3 to 5 cm. Up to 36 sensors can be found distributed radially and longitudinally, allowing a three-dimensional spatial pressure map to be drawn during deglutition. The graphic representation of this is what is referred to as esophageal pressure topography.

Whereas manometry is diagnostic for patients with named esophageal motility disorders, their presenting complaints are frequently vague and nonspecific. Hence, a complete workup including careful exclusion of other organ systems (cardiac, respiratory, peptic ulcer disease, and pancreaticobiliary disease) as the source of symptoms is paramount. In addition, attention to systemic symptoms of connective tissue disorders such as scleroderma is key as the surgical management of such patients requires specific modifications to avoid disastrous outcomes. With respect to the esophageal portion of the workup, a barium esophagram continues to be a highly useful road map to guide further investigations. A timed barium esophagram in which images are taken at 1, 2, and 5 minutes after the initial swallow may further characterize esophageal emptying and be particularly helpful in evaluating a patient with suspected achalasia. When the esophagus is thought to be the cause of the patient’s symptoms, upper endoscopy is necessary to rule out mucosal abnormalities and to provide improved visualization of the defects in question (stricture, hernia, diverticulum, esophagitis, masses). A computed tomography (CT) scan of the chest and abdomen is not uniformly required but may be helpful, particularly when there is suspicion of an extrinsic cause for the presenting symptoms. The addition of pH testing in the context of a documented esophageal motility disorder is necessary only when the motility disorder is thought to be the result of end-stage GERD as a means of documenting this.

Classically, esophageal motility disorders have been classified into primary and secondary causes. Primary disorders fall into five categories of motor disorders: achalasia, diffuse esophageal spasm (DES), nutcracker (jackhammer) esophagus, hypertensive LES, and ineffective esophageal motility (IEM). Secondary conditions result from progressive damage induced by an underlying collagen vascular or neuromuscular disorder; they include scleroderma, dermatomyositis, polymyositis, lupus erythematosus, Chagas disease, and myasthenia gravis. Whereas such a classification is rooted in the basic etiology of this collection of diseases, it does not help much with interpreting manometric results, nor is it helpful as a guide to treatment strategies. For this reason, we suggest an anatomic approach to classifying esophageal motility disorders based on involvement of the esophageal body or LES as this is the basis for understanding basic esophageal manometry and often the key to guide surgical therapy.

Motility Disorders of the Esophageal Body

Diffuse Esophageal Spasm

DES is a poorly understood hypermotility disorder of the esophagus. Under the Chicago classification, this is now called distal esophageal spasm . Although it is manifested in a similar fashion to achalasia, it is five times less common. It is seen most often in women and is often found in patients with multiple medical complaints. The cause of the neuromuscular physiology is unclear. The basic pathology is related to a motor abnormality of the esophageal body that is most notable in the lower two-thirds of the esophagus. Muscular hypertrophy and degeneration of the branches of the vagus nerve in the esophagus have been observed. As a result, unlike the normally organized peristaltic contractions typically seen with swallowing ( Fig. 42.14 ), DES esophageal contractions are repetitive, simultaneous, and of high amplitude.

The clinical presentation of DES is typically that of chest pain and dysphagia. These symptoms may be related to eating or exertion and may mimic those of angina. Patients will complain of a squeezing pressure in the chest that may radiate to the jaw, arms, and upper back. The symptoms are often pronounced during times of heightened emotional stress. Regurgitation of esophageal contents and saliva is common, but acid reflux is not. However, acid reflux can aggravate the symptoms, as can cold liquids. Other functional gastrointestinal complaints, such as irritable bowel syndrome and pyloric spasm, may accompany DES, whereas other gastrointestinal problems, such as gallstones, peptic ulcer disease, and pancreatitis, all trigger DES.

The diagnosis of DES is made by radiographic and manometric studies. The classic picture of the corkscrew esophagus or pseudodiverticulosis on an esophagram is caused by the presence of tertiary contractions and indicates advanced disease ( Fig. 42.17 ). A distal bird beak narrowing of the esophagus and normal peristalsis can also be noted. HRM findings in DES are a normal median integrated relaxation pressure (IRP), a measure of esophagogastric junction (EGJ) relaxation with swallowing, in addition to at least 20% premature contractions. Additionally, the distal contractile integral, which is a composite measure of distal esophageal contraction, is greater than 450 mm Hg·s·cm in DES ( Table 42.2 ). Correlation of subjective complaints with evidence of spasm (induced by a vagomimetic drug, bethanechol) on manometric tracings is convincing evidence of this capricious disease.

The treatment for DES is far from ideal as symptom relief is often partial. Traditionally, the mainstay of treatment for DES is nonsurgical, and pharmacologic or endoscopic intervention is preferred. All patients are evaluated for psychiatric conditions, including depression, psychosomatic complaints, and anxiety. Control of these disorders and reassurance of the esophageal nature of the chest pain that the patient is experiencing is often alleviating to distressed patients. If dysphagia is a component of a patient’s symptoms, steps must be taken to eliminate trigger foods or drinks from the diet. Similarly, if reflux is a component, acid suppression medications are helpful. Nitrates, calcium channel blockers, sedatives, and anticholinergics may be effective in some cases, but the relative efficacy of these medicines is not known. Peppermint may also provide temporary symptomatic relief. Bougie dilatation of the esophagus up to 50 or 60 Fr provides relief for severe dysphagia and is 70% to 80% effective. Botulinum toxin injections have also been tried with some success, but the results are not sustainable.

Surgery is indicated for patients with incapacitating chest pain or dysphagia who have failed to respond to medical and endoscopic therapy or in the presence of a pulsion diverticulum of the thoracic esophagus. Historically, a long esophagomyotomy is performed either through the abdomen or a left thoracotomy or video-assisted thoracoscopic approach in the chest is used. While some surgeons advocate extending the myotomy up into the thoracic inlet, most agree that the proximal extent generally should be high enough to encompass the entire length of the abnormal motility, as determined by manometric measurements. The distal extent of the myotomy is extended down onto the LES, but the need to include the stomach is not agreed on uniformly. A Dor fundoplication is recommended to provide reflux protection as the surgery itself interrupts the phrenoesophageal ligament and encourages reflux. Results of a long esophagomyotomy for DES are variable, but it is reported to provide relief of symptoms in up to 80% of patients.

Recently, several authors have reported their experience with the use of peroral endoscopic myotomy (POEM) in the treatment of motility disorders of the esophageal body. In this natural orifice approach, an operating endoscope is used to perform a mucosotomy and a submucosal tunnel is created. Through this tunnel, the circular muscular layer of the esophagus is visualized and divided, effectively performing an endoscopic myotomy. In one series, 73 patients with medically refractory motility disorders of the esophageal body, including nine with DES, underwent POEM and had a clinical response rate of 93%. Furthermore, in the 44 patients with repeat manometry available after POEM, all demonstrated resolution of the abnormal manometric findings seen on initial testing. Though POEM has most often been described in motility disorders of the LES, in particular achalasia (see Achalasia section below), this technology represents a novel surgical approach for performing a long esophagomyotomy in DES patients with early promising results.

Motility Disorders of the Lower Esophageal Sphincter